The present invention relates to a method for the formation of a silicon oxide film on the surface of a substrate. More specifically, the present invention relates to a method for the formation of a thick silicon oxide film that is free of cracks and pinholes and that is insoluble in organic solvents.
The formation of a protective film on the surface of a substrate is a technique in general use for its protection. In the particular ease of the electric/electronic industries, there has been a very substantial increase in the complexity of semiconductor devices and in topographical variations on the surface of semiconductor devices in association with recent increases in the degree of integration and layer count of semiconductor devices. An interlevel dielectric layer may be formed on the surface of a semiconductor device in order to planarize the topographical variations on the surface of the device, while a passivation coating can be laid down on the surface of a semiconductor device in order to protect it from mechanical damage, chemical damage, damage due to static, ionic contaminants, nonionic contaminants, radiation damage, and so forth.
Silicon oxide films are typically used for the interlevel dielectric layers and passivation coatings formed on semiconductor device surfaces. Chemical-vapor deposition (CVD) and spin-coating are examples of the methods used to form these silicon oxide films. As examples of methods for the formation of silicon oxide film on a semiconductor device surface by spin-coating, Japanese Patent Application Laid Open [Kokai or Unexamined] Numbers Sho 60-124943 [124,943/1985] and Sho 63-144525 [144,525/1988] propose the formation of a film of hydrogen silsesquioxane resin on the surface of the substrate (e.g., the semiconductor device, etc.) and subsequently heating the resin film-bearing substrate in air in order to form a silicon oxide film.
However, the methods proposed in Japanese Patent Application Laid Open Numbers Sho 60-124943 and Sho 63-144525 for silicon oxide film formation are not able to produce a silicon oxide film thicker than 0.6 micrometers (6,000 angstroms). As a result, these methods cannot completely planarize the topographical variations encountered on the surfaces of semiconductor devices, i.e., topographical variations or height differences in excess of 1.0 micrometers (10,000 angstroms). In addition, when the production of a thick silicon oxide film is attempted by these methods, cracks and pinholes are produced in the silicon oxide film and the reliability of the semiconductor device is drastically reduced.
The inventors conducted extensive research into the cause of the inability of the methods proposed in Japanese Patent Application Laid Open Numbers Sho 60-124943 and Sho 63-144525 to produce thick silicon oxide films. It was discovered that this inability is due to heating in air in order to obtain a 0% content of silicon-bonded hydrogen in the silicon oxide product. On the other hand, it was also discovered that the silicon oxide film could perform well as an interlevel dielectric layer or passivation coating on tile surface of a semiconductor device when the Si-bonded hydrogen content in the silicon oxide film product did not exceed 80% of the Si-bonded hydrogen content in the starting hydrogen silsesquioxane resin. Accordingly, the present invention was achieved as a result of extensive research into a silicon oxide film formation method that would be capable of producing a crack-free and pinhole-free thick silicon oxide film that could function as an interlevel dielectric layer or passivation coating on the surface of a semiconductor device and that would also be able to thoroughly planarize the topographical variations on the surfaces of semiconductor devices.
The present invention takes as its object the introduction of a method for the formation of an organic solvent-insoluble, crack-free and pinhole-free silicon oxide thick film by the formation of a hydrogen silsesquioxane resin film on the surface of a substrate and then heating this resin film-bearing substrate.